Strange Lag issues playing nba 2k11 on ASUS N61jq Laptop

Hey all having this minor issue whilst gaming with nba 2k11 on mid to high settings i get these strange 20 - 30 sec lags as for the lag its like a spike,the game runs smooth for roughly 4-5 min then totally does action replay style lags. then everything returns to normal again,it happens every 5 min to,can anyone perhaps identify the culprit,specs below,cheers
One thing to Note when i had 2k10 installed on the laptop it ran smooth on max settings,problem has occured since 2k11 got installed

Processor: Intel Core i7-720QM (1.6 GHz)
RAM Installed: 4Gb
Graphics Card: Mobility Radeon HD5730 1GB GDDR3 dedicated
Operating System: Win 7 32Bit

try updating your VC drivers, also try tweaking you cfg. you have a powerful machine, tweak your CPU_LOGICAL THREADS. that's what i suggest.

the big issue was the drop in FPS it would drop from 60 to 15 fps every 5 min,whateva i done to the ati catalyst has actually stopped it now...i disabled it at first,re enabled it now,and FPS have not dropped at all anymore,so hopefully it stays like this